Having twins teaches you one thing, for sure - you need two of everything to prevent all-out war. But when you have two additional kiddos in addition to the twins, you eventually learn that you sometimes need four of everything.
And such is the case with plasma cars.

Our driveway has a great slope to it, so they can actually get going pretty fast by the time they hit the grass at the bottom.

Bates is Mr. Cautious, rarely lifting his feet off the ground. But the other three...that's a different story. They definitely have the need for speed!